Control-gear for hydraulic transmission.



W. E. MAGIE. coNmoI. GEAR Fon HYDRAULIC TRANSMISSION.

APPLICATION FILED OCT. 4| I9l5.

1,299,751, Patented Apr.8,1919.'

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CONTROL GEAR4 FOR HYDRAULIC TRANSMISSION. APPLICATION FILED OCT. 4| |9I5.

Patentd Apr. 8, 1919.

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.APPLICATION FILED OCT. 4. |915.

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WILLIAM E. -MAGIE, 0F EVANSVILLE, INDIANA.'

CONTROL-enen Fon H'aDnAULIc transmission.

To all 'uihm z'may concern.' d Be it known that ,WnmrAM E. MAGIE, a

'citizen of the Un ted States, residing at i Evansville, in the county of Vanderburg and State'of Indiana, have invented a certain new and useful Improvement in Control- `Grears for Hydraulic Transmisslons, -of

- system.l 4Other objects of my invention will this type o appear in the specication; `I have illustrated my invent1on as applied to a hydraulic transmission of the so-called axial typein which a series of pump cylinders arranged axially forces the motive fluid into a series of motive cylinders also Iarranged axially. The motive fluid-thus circulates through the system made up of the motive and pump system and controlling ,fand communicating members. The amount of work done by the pump is a' pressure la ainstwhich it disdharges. In machine the pump is a so-called variable, displacement pump. The pistons are caused to reciprocate in the cylinder by means of a rotating inclined swash plate. 'The displacement of the pump for each I revolution depends on the inclination of the 40 swash plate.' If the swash plate is pependicular to the rotating drive shaft. no discharge takes place because no piston movement occurs. As the inclination of the swash `plate with respect to the axis of the shaft in- -^creasesethe stroke of each piston increases creased.-

and the dis lacement of the pump thus is inlhe system is a closed systemand the swash plate may be tilted in either direction so as to give a forward or reverse movement of the motive fluid through the system.

i `Hydraulic transmissions are rated to give their normal power out-put at a certain predetermined munber of revolutions and at a certain predetermined pressure. This prersure I call P? highest working` pressure -at. which the maspeication of' Letters Patent. Application viled October 4, 1915. Serial No. 53,861.

gears for hydraulic transmissionsl function of its discharge and the and it may be deined as the through the motor Patented Apr. 8, 191.9.

chine is intended to operate when handling the` maximum quantity of motive fluid. Hydraulic transmissions, however, are frequently subject to severe overloads such as in starting `and reversing machinery and the like. In order that they may carry s uch overloads they aredesigned to operateunder some circumstances ata maximum overload presr sure which I have called P1. This is the highest pressure to which it is consideredsafe to subject the machine. It has been customary in' the past to provide hydraulic transmissions with a safety valve set for this overload pressure P1 and so one object of my invention is to provide means which may be substituted for the safety valvewithout any danger to the lmachine.

Generally speaking, P1 would be about twice as great as P2. Assuming for instance that the prime mover is adapted to work at its best at 1000 R. P. M. it would be direct connected to the pump shaft and the pump would operate at 1000 R. P. M. If the machine were designed to displace -cu.`inches of motive fluid per revolution at 500# per square inch pressure we would have a machine rated at 125-H. P. If this machine wereprovided with a safety valve the valve i would be set to release at about 1000:]1; p er square inch se as to give the machine a sultable margin of safety to enable it to move or take momentary :over loads and starting loads. f A f) If the device is equipped with a safety valve there is nothing to .prevent the oper- Aator from tilting the swash .plate so as to give the maximuinfpump stroke 100-cu. inches' of` water per""revolution. lIf he no longer manipulates the lever and leaves 1t 1n -this position any excessive resistance may run the pressure to 'over 1000# per square inch, whereupon'the safety valve opens/and the motive fluid instead of'being 4,pumped `andk performing use work will be forced through the safety valve controlled relief aperture. All ofthe energy conveyed by this 'luid,`whi ch` if the motor were operating useful work, will be converted into heat as the iiuid passes out through the relief o ening. This will cause overheating. and oiling of the motive iuid and possiblydestruction of the machine. The hydraulic motor if the resistance continued would, of course, during this time-be at restand the prime mover would continue its movement against the heavy over load ybeing thus compelled to double its rate of capacity.

In my preferred form of improvement of control the safety valve is eliminated and a control gear Vprovided whose function is to prevent the discharge by the pump of motive fluid in such quantity or under such a pressure as not to conform to the two following requirements:

(l) The pressure of the oil must at no time eXceed the maximum safepressure P1.

A(2) The power delivered by the pump (function of pressure times displacement) must never exceed the power which the prime mover is designed to furnish.

This control gear automatically takes care of both of these points, thus preventing both overloading and overheating of the machine, preventing waste of power, and only interfering with the manipulation of the operator when such interference is necessary to accomplish these objects. In other words, it leaves the operator entire freedom of action but makes the machine fool proof.

My invention is more or less diagram` matically illustrated in the accompanying drawings, wherein Figure 1 is a plan view;

Fig. 2 is a longitudinal part section and part elevation on a plane at right angles 4to the plane of Fig. 1 along the line 2-2 of Fig. 1.

Fig. 3 is a section on the line 3 3 of Fig. 1.

Fig. 4 is a section along the line 4 4 of' Fig.

Fig. 5 is a section along the line 5 5 of Fig. 3. i

Fig. 6 is a detail section along the line 6 6 of Fig. 3.

Like parts are indicated by like letters throughout the several figures.

A is a pump housing; A1 a motor housing, and A2 a connection between them. A3 is a pump shaft driven by any suitable prime mover not here shown; A4 the motor shaft driving any suitable resistance not here shown. At'7 is a motor cylinder barrel containing cylinders A6 and pistons A7 which coperate to drive the shaft A1 by any suitable connections not here illustrated. Aa is a pump cylinder barrel containing the cylinders A and pistons A10. These pistons are driven through the medium of connecting rods- A11 from the rotating swash plate A12 which plate is drivenby the shaft A3 through the universal joint A14.

B is avalve plate interposed between the opposed ends of the cylinders A, A9. Through it are the two separate ports B1, B2. Either one of` them may be an exhaust, the other a discharge port depending on the position of the inclined swash plate. If the h rotates in a counter-clockwise direction then with the swash plate tilted in the position shown in full lines the port 2 will be the pressure port andthe port B1 theintake port. If the swash plate were tilted in the opposite direction 'the opposite would be thel case. B3 is a control cylmder mounted in the housing A2. In it is a piston B1 free to reciprocate therein. This piston B1 is mounted on a. piston rod B5 which port B1 to the righthand end .of the cylin# der B3. B14 is a passage leading from the exhaust port B2 to the left-hand end of the cylinder B3.

The cradle A13 is provided at either end with stub end shafts C, C1 in bearings in the housing A. C2 is a hub mounted for rotation on the trunnion C2 and carrying a hand lever C3. The lever C4 is mounted for rotation with the hand lever C3y and provided with a ball C5 in rotatable engagement with socket C on the rod C1. The rod C7 at its opposite end is connected by a ball and socket joint D1 to one end of the cross lever D. The cross lever is' pivoted at D2 to the extension B50 on the piston rod B5, and is connected at its other end by a ball and socket joint D3 to a rod C8 similar to the rod C7. The hub C is keyed to the shaft C1 and carries a lever C1-whieh has a ball C11 in rotatable engagement with a socket C12 on the opposed end of the rod C8. It will be noted that the axis about which the hand lever and the cradle rotate is also the parting from the spirit of my invention and I wish, therefore, that my drawings be regarded as in a sense diagrammatic.

The use and operation of my invention is as follows With the prime mover in o-peration rotating the shaft and thus the swash plate and with the swash plate in its neutral position perpendicular tothe shaft the piston barrel, the swash plate cylinders and all the moving parts of the pump will be in rotation` but since the swash plate is not inclined to the shaft the pistons will not move inthe cylinders and the pump will not then displace any lnotive Huid. he operator in order to start the load will swing the hand lever away from the central position. This will cause the cross lever -to vrotate about its pivotal point en the end of the control piston rod in a clockwise direction thus rotating the arm keyed to the stub end shaft and rotating the swash plate into the position shown for forward movement. The pistons will immediately commence to move in their cylinders and pump the motive fluid into the motor. The motor will then commence to move the load connected 'to it. The load being at rest there will be an immediate increase in pressure in the system. This pressure under ordinary circumstances will run up above the normal working pressure. When it does this the pressure in the cont-rol cylinder will force the control piston to the left against the tension of the spring. Since the manual control lever will not be moved the cross lever will rotate about its pivotal connection with the hand lever and the swash plate will be moved by the rotation of the free end of the cross lever back toward the central position. This movement may. continue as the pressure rises until the pistou has moved suiiieiently toward the end of the cylinder when the swash plate will have been returned to the zero position.y Under ordinary circumstances, however, as the piston'movement gradually occurs toward the end and the swash plate is gradually tilted the decrease in displacement of the pump will be sutlicient to hold the pressure down to a safe maximum and as the meten, gradually takes up this lo-ad and accelerates it the pressure will decrease.- As this pressure decreases the spring will gradually move the piston back to the central position until when the load is under way the pump will again operate at its peint of maximum etticiency; vlz: with maximum displacement at its predetermined pressure.

It 'during operation any sudden resistance should be encountered the same thing will happen. As the pressure rises the piston will be moved by pressure suilicient to overcome the spring and to' graduallvtilt the swash plate, and decrease the displacement of the pump so as to hold the pressure down below the danger point..

The same situation exactly will prevail if the hand lever were shifted in the opposite direction. The cross lever would still rotate about its pivotal point and would still be free to control the inclination of the swash plate .with the hand lever at rest when the piston is moved bv the pressure. ln caseof sudden reversal, if; for instance the operator moves the lever from the extreme left to the extreme right-hand position suddenly rocking the awash plate vtoward the reverse position.

through the zero position to the reverse, the changes in pressure will be eared for in substantially the same manner. If this reversing movement is made suddenly, the direction in which the pump would circulate the motive fluid would be instantly reversed. If the transmission is carrying a heavy inertia load the pressure in the ports B1 and B2 will reverse. if the yoke is moved toward the reverse position any faster than the load driven by 'the transmission will slow down from its own Jfrictional resistance, and the back pressure; For instance, let us assume that the hydraulic motor carries a heavy flywheel, running at maximum forward speed with the yoke in position Y1.

If the operating lever is suddenly thrown to the opposite position the yoke will`suddenly begin to follow the operating lever, starting toward the position Y2. As soon as it has moved a very short distance it. shortens the stroke of the pump so that. the pump is no longer delivering` oil to the hydraulic motor at. the speed corresponding to the speed at which the motor and iiywheel are running. The motor will therefore be passing oil through into the exhaust port faster than the pump with its reduced stroke can receive it. This instantlv reverses the functions of the ports, raising a pressure in the former exhaust port and reducing the pressure in the former pressure port. In this condition the hydraulic motor is driving the pump, and the pressure in the exhaust port is acting to check the speed of the fly-wheel and gradually reverse its motion. The amount of this pressure in the exhaust port will depend on the inertia ot' the iiy-wheel tobe reversed, and on the rate at which the operating lever is moved During the time of reversal the energy of the {iv-wheel will be partly dissipated through the frictional resistance of the mechanism. The remainder of the kinetic energy must be transerred to some other moving body. This is done through the pressure of thel liquid in the exhaust port. reacting against the pump pistons and tending to increase the speed of the pump and its prime mover. It the inertia of the pump and prime mover are large and their speed variations therefore moderate, a considerable interval of time will be. occupied in the transference of the kinetle energy necessary to the reversal. The reversal may be accomplished by a slow uniform movement of the operating,lr lever, gradually shortening the stroke of the pump. The operating lever may -be moved A be moved faster than this the pressure will rise above P2 toward the maxlmum pressure P1, in which case the spring will be some-- quickly rise to P1, pushing the piston to the cylinder would extreme right hand end of the cylinder, and bringing the tilting yoke almosti' to its original position Y1, from which the reversing movement was started, notwithstanding that the hand lever remains at full reverse. When this condition is established the automatic control takes y'entire charge of the completion of the reversal, the spring pushing the piston back toward central position as the pressure vgradual change in speed of the hydraulic motor and ily-wheel. returned half way to the middle position the motor shaft and iy-wheel have come-to restand are justbeginning their accelera.

tion in the reverse/direction, the speed again increasing and iinally reaching full reverse Speed as the piston returns to middle positlon and the pressure has fallen to P2.

In the case of afplaner where the internal friction is comparatively large and the speed of the heavy parts comparatively slow such a reversal may take place very quickly, as the kinetic energy to be transferred to the prlme mover, etc., is smallm On the other hand, the reversal of a large fly-wheel would be very slow. In either case, however, the hydraulic transmission itself is absolutely protected from excess of pressure and from overheating. Sucha transmission could be placed in a motor railwaycar or locomotive` interposed between the prime motor and driving wheels. Assuming a constant speed prune mover, as an electric motor, gasolene englne, or high speed steamA engine, it would only be necessary when starting from station for the ogerator to immediately throw the lever into ll speed ahead. `The control promptly compensate this movement and automatically keep the transmission working' at the highest practicable pressure to accelerate the'train in the least posslble time.

Experience shows that with the above control it is ,necessary to provide a prime mover which Will deliver 50% above the normal rated power of the transmission, to enable the operator to place the control lever at full speed, and let the entire apparatus adv just itself automatically to load conditions.

lf prime mover is acoustant speed machine the pump w1ll deliver the quantity of oil exhaust port would= gradually falls, due to thel When the piston has.

or yk' is tilted and the displacement of the plate decreases the speed at which the motor operates will also decrease and "this, .of course, will give the operator warning that he is working above the rated capacity of the machine. If he does notaetaccordingly and the pressure continues to increase the pump will be finally drawn to a standstill.

The Aautomatic friction control rocking` means for the hand lever insures that as soon as the lever is released bythe hand of the operator it remains in the position left by him so `that when the automatic control operates the hand lever controlled or positioned fulcrum of the cross lever will not varythus the operation of the automatic control does not depend in any way upon the hand lever.

I claim: 1. The combination with a transmission mechanism of a driving shaft therefor, means for controlling the operation of the transmission mechanism, a floating lever and a connection between it and such controlling means, a manually operated control lever and a connection between it and the floating lever, a member movable in response to conditions prevailing within the transmission mechanism and a connection be.- tween it andthe floating lever.

2. A hydraulic transmission comprising a pump and means for varying its displacement. a motor and circulatory system includ-` ing the pump and the motor, a control cyllnder in communication with said system, a

gisten therein and an operating connection etween it and the displacement Varying means, a manual control member and a connection between it and the displacement means, said piston connection and said manual control ,being each free to operate the displacement varying reans independent one from the other.

3. vA hydraulic transmission comprising a pump and means for varying its displacement, a motor and circulatory system including the pump and the motor, a control cylinder in communication with said system, a piston therein and an operating connection between it and the displacement varying means and yielding means for resisting the movement of said piston, a manual control member anda connection between it and the displacement varying means` said piston connection and said manual control being each tree to operate the displacement var ving means indelmndently one from the other.

4. The combination with a' pump ol a driving swash plate mounted o rock about an axis perpendiiular to the axis o'lE the pump of means for rocking it comprising a lever mounted for movement therewith, a floating lever connected thereto. a hand control member and connection between it andA the floating lever and a normally fixed fulcruni for the floating lever.

rl`he combination with a pump of a driving swash plate mounted to rock about an axis perpendicular to the axis of the pump of means lor rocking it comprising a leverv mounted for movement therewith, a floating lever connected thereto, a hand control member and connection between it and the floating lever, a normally fixed fulcruni for the floating lever and means responsive to the pressure in the pump for displacing said fulcrum.

G. The combination with a pump of a driving swash plate mounted to rock about an axis perpendicular to the axis of the pump of means for rocking it comprising a lever mounted for movement therewith, a floating lever connected thereto, a hand control member and connection between it and the floating lever, a normally fixed fulcrnm for the floating lever and means responsive to the pressure in the pump for displacing sa1d fulcrum, said means comprising a control cylinder and hydraulic connection be tween it and the pump system, a piston therein and a connection between it and the fulcrum.

7. The combination with a pump of a driving swash plate mounted to rock about an axis perpendicular to the axis of the pump of means for rocking it comprising` a lever mounted for movement therewith, a floating lever connected thereto, a hand control member and connection betweenit and the floating lever, a normally fixed fulcrnm for the floating lever and means responsive to the pressure in the pump for displacing said fulcrum, said means comprising a control cylinder and hydraulic connection between it and .the pump system, a piston therein and a connection between it and the fulcrum and yielding means for resisting the movement of said piston.

' 8. The combination with a pump of a driving swash plate mounted to rock about an axis perpendicular to the axis of the pump of means for rocking it-comprising a lever mounted for movement therewith, a floating lever connected thereto, a hand control member and connection between it and the floating lever anda normally fixed fnlcrum for the floating lever, 'the fulcrum besaid fulcrmn, the fulcrnm being located substantially'- at theA mid point of the floating lever.

10. The combination with a pump of a driving swash plat-e mounted to rock about an axis perpendicular to the laxis of the pump of means for rocking it comprising a lever mounted for movement therewith, a floating lever connected thereto, a hand control member and connection between it and the floating lever, a normally fixed fnlcruni for the floating lever and means responsive to the pressure in the pump for displacing said fnlcrum, said meanscomprising a control cylinder and hydraulic connection between it and the pump system, a piston therein and a connection between it and the fulcrum, the fulcrum being located substantially at the mid point of the floating lever` Il. The combination with a pump of a driving swash plate mounted to rock about `an axis perpendicular to the axis of the pump ofmeans for rocking it comprising a 10o lever mounted for movement therewith, a floating lever connected thereto, a hand control member and connection between it and the floating lever, a normally fixed fulcrum for the floating lever and means responsive to the pressure in the'pump for displacing said fulcrum, said means comprising a control cylinder andhydraulic connection between it and the pump system, a piston therein and a connection between itv and the fulcrum and yieldin means for resisting the movement of sa1d piston, the fulcrum being located substantially at the mid point of the floating lever.l

12. The combination with a pum and means for driving it of a plurality o separate independently acting control means for varying displacement w1thout varying the speed'thereof, one of said control means being manually operated, the other being automatic, said control means being mutually independent both in operation and in their re-action upon the pump.

13. The combination 'with a pump and means for driving it'of a plurality of sepa- 125 rate independently acting control means for s varying displacement without varying the speed thereof, one of said control means being manually operated, the other being operated responsive to pressure variationsQ in the pump, said control means being mutually independent both in operation and in their re-action upon the pump.

` 14. In a hydraulic transmission comprising a pump and means for driving it, means for controlling the operation of the tra'nsmission mechanism, comprising a manually operated lever, a control lever directly cnnected to the pump and normally responsive to the manually operated lever, and automatic means responsive to pressure within the pump for varying the response of the control lever to the position of the manually operated lever, said automatic means and the manually operated lever being lmutually independent both in operation and in their reaction upon the pump.

15. In a hydraulic transmission comprising a pump and means for driving it, means for controlling the operation of the transmission mechanism, comprising a manually operatedlever, a control lever directly connected to the pump responsive to the manually operated lever, a connection between the two levers, and automatic means responsive to the pressure in the pump, for varying the position of the control lever, independent of the position and operation of the manually controlled lever.

16. In a hydraulic transmission comprising a pump and means for driving it, means for controlling the operation of the transmission mechanism comprising a manually operated lever, a control'lever directly connected to the pump and directly responsive to the position of the manually operated arm and each of the levers, and automatic means. responsive to the pressure 1n the .pump for varying the position of the rocking arm and the control lever, independent of the position and operation of the manually controlled lever.

17. In a hydraulic transmission comprising a pump and means for driving it, means for controlling the operation of the transmission mechanism comprising a manually operated lever, a control lever directly connected to the pumpI and normally responsive directly to the manually operated lever, a rocking arm interposed between the two levers, connections between the rocking arm and each of the levers, a normally fixed fulcrum for .the rocking arm, and automatic means, responsive to the pressure in the pump for varying the position of 'the fulcrum of the rocking arm, independent of the position of the manually controlled lever.

In ,testimony whereof I'aix my si nature in the presence of two witnesses this 10th day of September, 1915.

WILLIAM E. MAGIE.`

Witnesses:

W. J RYAN, E. K. SWIGART. 

